For someone, something (theme mi-) to be at the extreme edge of a drop-off, or slightly protruding beyond it, as at the edge of a cliff, a stone-wall terrace, a table top, a doorway of a house on foundation piles.
For someone (actor -um-) to place something (theme i-) at the extreme edge of a drop-off (loc ref), or slightly protruding beyond it, as to place stones in a stone wall in line or slightly protruding beyond other stones, an object at the edge of a table.